Manual of physiology for students and practitioners / by H. Willoughby Lyle.

  • Lyle, H. Willoughby.
Date:
1911
Catalogue details

Licence: In copyright

Credit: Manual of physiology for students and practitioners / by H. Willoughby Lyle. Source: Wellcome Collection.

Provider: This material has been provided by The University of Leeds Library. The original may be consulted at The University of Leeds Library.

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    achromatic spindle is probably formed from the two centrosomes and the achro- matic substances in the nucleus. (c) Cleavage.—Each chromosome moves to- wards the centre of the achromatic spindle, and splits longitudinally into two daughter threads. {d) Monaster or Star.—The achromatic spindle becomes longitudinal and the split chro- mosomes arrange themselves in a star- shaped manner around the equator of the spindles. {e) Metakinesis or Divei-gence. — The polar bodies or centrosomes at the ends of the spindle appear to attract the' daughter V's which move along the tibres of the spindle. It may be that the V's are pulled into their new position by the contraction of the fibres of the spindle to which they are attached. (/) Diaster or double Star.—The V-shaped fila- ments are conveyed to the centrosomes of the spindles and the fibres of the spindle split at the equator. The bio- plasm of the cell now commences to split. {g) Dispirevi or double Skein.—An open skein is formed in the daughter nuclei, later the chromosomes unite to form a closed skein in each daughter nucleus. {Ji) Reticulum.—The resting stage of each daughter nucleus ; the bioplasm of the original cell having split at the same time as the nucleus divided, two resting cells are consequently produced. A nuclear membrane forms around each daughter nucleus, and the remains of the spindle gradually disappear. The time occupied by karyokinesis varies from a half an hour to three hours. Many of the changes described may be seen in the cells of the epidermis contained in a section of a newt's tail.